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April 24, 1928. I 1,667,678

I E. RIECKE ELECTRIC ROLLING MILL DRI VE WITH LEONARD CONTROL Filed May 20. 1926 Invenaor: Ernst, Riec K8;

His Attorney.

Patented Apr. 24, 1928.

UNITED STATES 1,667,678 PATENT OFFICE.

ERNST RIECKE, OF CHARLOTTENBURG. GERMANY, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

ELECTRIC ROLLINGMILL DRIVE WITH LEONARD CONTROL.

Application filed May 20, 1926. Serial No. 110.558. and in Germany J'une 30, 1925.

In rolling mill trains or stands which ordi uarily work together and of which one is required to be driven at a variable :-l)t8(l. and the other at a constant speed. such as is. {oi-example, the case with medium iron mills. it has been the practice heretofore to provide separate drives for the stands so that the roughing mill stand was driven by a. normal three phase motor while the finishing stand belonging to it was provided with a variable sJeed drive. 'it-h this arrangement the nishing stand was ordinarily driven by any-of.-the wcil known variable speed sets or by a dircct current motor with field regulation.

Recently. as the demands particularly with respect to production continually in crease. resort has been had to providing the finishing stands with Leonard drive, as for example, in the. ease of medium iron mills with separate roughing mill stand. thus achieving the well-known advantages of an unlimited speed regulation. The roughing stands retain, as hitherto, three phase drive without speed regulation.

In the case of such drives it is possible, according to the invention, to obtain a substantial reduction in the cost of the plant and a better overall eliiciency by simultaneously driving the roughing mill stand, in addition to the Leonard generator for the finishing stand, from the shaft of the driving motor for the control converter. If it is a case of Leonard control with flywheel equilization (Ilgner converter) it is possible to obtain a further reduction in the cost of the plant because the common flywheel of the Ilgner converter produces an equalization of the load variations of both stands and a. separate flywheel for the roughing stand becomes unnecessary. In addition. a better equalization of the load variations is obtained by the flywheel in view of its large stored energy.

Since the speed of the Ilgner converter is, as a rule, higher than that desirable for the roughing mill stand the drive is suitably transmitted through reduction gearing.

There are also cases in which two rolling mill stands are required to work alternately, the one stand being driven at a constant speed and the other stand driven by 21 Leonard drive at a variable speed. In this case the arrangement can also be chosen in the manner described above. This combination has the advantage that the Ilgner The .ro'u'ghing; rnill "train or}; stand V I is venlfih ieug oo d ilg 'aizi g y h driving motor M of theflllgner converter, .Wh h .i fl difi sted, a i itbreerph se. ,mp supplied with paw-imam the 'source" A through the switch B. The common flywheel S is situated between the stand V and the motor M. The generator G feeds the motor M of the finishing stand F connected in Leonard fashion.

The motor M is indicated as of the adjustable speed type havin the adjustable resistors R included in the rotor circuit thereof. However. the invention is not limited to an adjustable speed 'alternating current motor since a squirrel cage type motor may be used instead. The stand V may be disconnected from the motor M and flywheel S opening the clutch C, the flywheel and stand may be disconnected from the motor M by opening the clutch C and the motor M may be disconnected from the stand F by opening the clutch C The generator G is provided with a field winding f which is separately excited from the direct current source of supply K. The direction of the excitation of this field winding is governed by the reversing controller T and the value of the excitation is governed by the rheostat 1'. The field winding f is also separately excited from the source K and the value of the excitation is governed by means of the rheostat r.

In case it is desired to drive merely the roughing stand V, the controller T is operated so as to deenergize the generator field winding f and the arm of the rheostat 1" is operated so as to disconnect the motor field winding f from the source is. In this case the motor M will not be driven while the roughing stand V is being driven by the motor M. In case it is desired to drive the finishing stand F and not drive the roughing stand V. the clutch C is opened. thereby disconnecting the stand V from the motor M.

It is presumed in this latter case that the controller T and rheostats 1- and r are suitably operated so as to energize the generator and motor separately excited field windings at the proper value. for the. desired speed of the stand F.

What I claim as new and desire in secure by Letters Patent of the United States is 1. In combination in a drive for rolling! mills and the like, a substantially constant speed stand, an alternating current motor for driving the same, a variable speed stand. and a Leonard drive for said variable speed stand comprising a separately excited generator driven by said motor and a separatel excited motor connected to said variable speed stand and supplied with armature current from said generator.

2. In combination in a drive for rolling mills and the like. a substantially constant speedstand, an alternating current motor for driving the same, a flywheel driven by said motor, a variable speed stand, and :1 Leonard drive for said variable speed stand neezevs comprising a separately excited generator driven by said motor and a separately excited motor connected to said variable speed stand and supplied with armature current from said generator.

3. In combination in a drive for rolling mills and the like. .a substantially Constant speed stand, an alternating current motor for driving the same. a flywheel driven by said motor. a connection between said stand and said motor arranged to connect said motor in driving relation with said stand or disconnect the same therefrom, a variable speed stand. and a Leonard drive for said variable speed stand comprising a separately excited generator driven by said motor and a separately excited motor connected to said variable speed stand and supplied with armature current from said generator.

In witness whereof, I have hereunto set my hand this 27th day of April, 1926.

ERNST RIECKE. 

